1. Field of the Invention
This invention concerns installations of "air bag" safety systems in passenger compartments of vehicles adopted to transport passengers such as cars and trucks.
2. Description of the Prior Art
"Air bag" safety systems comprise an inflatable enclosure stored in folded condition in a storage site within a passenger compartment, which is very rapidly inflated when a severe vehicle collision is detected so as to be deployed in a position to cushion the impact of the driven or passenger against the interior surfaces.
The storage site for the folded air bag is usually covered with a deployment door to be protected, and in many designs, the deployment "door" is forced open by the inflating air bag.
The level of resistance to opening the door affects the performance of the air bag system since it may affect the time required for full deployment. At the same time, the door must be secured against tampering.
U.S. Pat. No. 4,893,883, issued on Jan. 16, 1990, for "Closure for an Air Bag Deployment Opening"; and U.S. Pat. No. 4,989,896 issued on Feb. 5, 1991, for "Double Door Closure for an Air Bag Deployment Opening" show locking tabs which are sheared open under the pressure of the inflating air bag, allowing the deployment door or doors to hinge open. See also U.S. Pat. No. 5,082,310 issued on Jan. 21, 1992, for "Arrangement for Providing an Air Bag Deployment Opening".
It has heretofore been proposed to design the trim piece behind which the air bag is stored so that the deployment door is not visible. The trim piece structure must at least in part be fractured along a door seam to allow the air bag to deploy out into the passenger compartment.
In an effort to minimize the force required, it has heretofore been proposed to use linear energy generating elements, such as detonator cord, pyrofuse, explosive coatings, etc. to cut through the substrate and/or skin and foam just prior to air deployment, and form a door through which the air bag can deploy.
See U.S. Pat. No. 5,080,393 issued on Jan. 14, 1992, for "Method and Apparatus for Forming an Air Bag Deployment Opening"; U.S. Pat. No. 5,217,244 issued on Jun. 8, 1993, for "Arrangement for Forming an Air Bag Deployment Opening"; and U.S. Pat. No. 4,991,870 issued on Feb. 12, 1991, for "Method and Arrangement for Forming an Air Bag Deployment Opening in an Auto Interior Trim Piece" for examples of this arrangement.
In each of these cited patents, the energy releasing element direct heat and pressure onto the trim piece structure to cut at least the overlying skin.
Such direct release of energy requires that the element be carefully designed in order that the outward blast does not present a hazard to any person in the passenger compartment.
The object of the present invention is to provide an arrangement for creating a deployment opening in a trim piece which does not involve a visible deployment door and which does not involve directing explosive or heat energy through the trim piece and into the passenger compartment.